1. The Field of the Invention
This invention relates to communication systems that are used by computer equipment to communicate data across public or private telephone lines. More particularly, the invention relates to a system and method for connecting and interfacing a communications device to a telephone line via a telephone set.
2. Related Technology
3. The Relevant Technology
Increasingly, users of personal computers and related equipment rely on the ability to utilize public and private telephone lines to transmit and receive data. This capability dramatically increases the value and usefulness of the computer, as well as the overall productivity of the computer user. As the availability of personal communications equipment, remotely accessible public and private networks, databases, computer-based bulletin boards and related computer services continues to increase, the need to have reliable and consistent access to telephone communication links will continue to grow.
As is well known, equipment such as personal computers and facsimile machines communicate across telephone lines equipment known as a xe2x80x9cmodem.xe2x80x9d The term modem is an acronym derived from the phrase xe2x80x9cmodulator-demodulator,xe2x80x9d which is descriptive of the basic function performed by the modem. A modem enables digital equipment to interface with the public telephone network, which is designed to carry analog type xe2x80x9cvoicexe2x80x9d signals. The modem accomplishes this by modulating the outgoing digital data so that it is compatible with the analog signal format used by the telephone network. Similarly, the modem reverses the process by demodulating incoming analog signals from the telephone network into the digital signal format that is compatible with most computer equipment.
The standard telephone line, whether public or private, utilizes a two-wire communication pathxe2x80x94wherein one wire forms a transmission path and the other forms a receive path. Similarly, most communication devices, including modems and telephone sets, have a two-wire transmit path and a receive path that corresponds with the two-wire telephone line. Ideally, the transmit wire and the receive wire of the communication device (often referred to as the xe2x80x9ctipxe2x80x9d and the xe2x80x9cringxe2x80x9d lines) are connected directly to the corresponding two wires of the telephone line via a RJ-type module and plug/cable detachable interface arrangement. However, under many circumstances such a direct interface is either impractical, inconvenient and/or not physically or electrically possible.
Typically, a communication device such as a personal computer modem, does not have access to a separate and dedicated phone line reserved solely for data communications. This is especially true in telephone systems which utilize a central Private Branch Exchange (PBX), where many telephone lines are serviced by a central PBX controller. In such an arrangement, which is common in many offices, hotels, schools and similar buildings, the telephone equipment is not connected directly to the public telephone network. Rather, the PBX acts as an automatic switching system to interconnect communication devices, such as telephone sets, within a building or campus of buildings. When communication is required outside of the building, the PBX acts as a multiplexing gateway to the public telephone network. Consequently, the providing of dedicated telephone lines for modems is often an impractical and inefficient use of a PBX system, and could result in a need for additional public telephone lines that may not be used to full capacity.
Thus, in a typical telephone environment, a user may desire to have both voice and data communication capabilities over a single telephone line. Often however, it is difficult to share a line between a modem and a telephone set. For instance, in many PBX systems a telephone set, specifically designed for use with the particular PBX controller, must always be coupled to the telephone line. Decoupling of the telephone set from the line may disrupt the PBX controller and thereby prevent proper line selection for outgoing communications. As such, a user cannot simply unplug the telephone set from the phone jack and plug in the computer modem to access the public telephone network.
Also, some PBX systems may utilize modular phone jacks that are not of a conventional size and/or shape, or which utilize a different electrical interface. Often, such an arrangement will not be compatible with the standard RJ-type connector found on many modems, and the user cannot physically and/or electrically interconnect with the telephone line. A similar problem occurs when there is not a modular wall/jack connector available to the modem user. For instance, some office buildings and many hotel rooms have telephone sets that are hard-wired directly into the telephone line, rather than via a RJ-type modular plug and jack arrangement. Again, the modem cannot be physically interconnected with the telephone line, and it is therefore rendered useless.
Even in those instances where a single telephone line can be used both for both voice and data transmissions, the line must be physically shared between the telephone set and the modem Under this arrangement, the telephone set must be physically disconnected from the telephone line in order to connect the modem, and vice-versa. This process is time consuming, awkward and inefficient, and does not allow an effective or efficient sharing of the single phone line.
It will be appreciated that the above problems to gaining access to the telephone network can prevent the effective use of any communication device. However, such difficulties are especially problematic for the increasing number of users of portable computers (referred to variously as laptop, notebook, subnotebook or palm-top computers), for whom the ability to access the public telephone network is extremely important. These types of personal computers are often equipped with internal modem and facsimile devices, and, due to their mobility, must be capable of accessing telephone lines under a wide variety of circumstancesxe2x80x94including those discussed above.
Solutions to the problems encountered when attempting to access the public telephone network for data communications have heretofore not been entirely satisfactory. As mentioned above, in the typical telephone set the telephone base uses a two-wire communications connection that is coupled directly to the two-wire telephone line. The telephone set also includes a handset, which is coupled to the telephone base via a handset cord. Usually, the handset cord has a modular RJ-type plug at one end, which detachably mates with a handset jack mounted in the telephone base. The telephone base includes circuitry that converts incoming and outgoing signals from the two-wire telephone line connection to a four-wire connection at the handset jack. This is because the wiring between the base and the handset includes a pair of microphone lines (i.e., a pair of transmitting lines) and a pair of speaker lines (i.e., a pair of receiving lines), which collectively couple the base hardware to a microphone and speaker mounted in the handset.
Given this standard arrangement, one solution to the above mentioned problems has been to provide an interface adapter that allows the modem to connect to the telephone line via the telephone set. Under this approach, the telephone base remains interconnected with the two-wire phone line, and the modem connects, via the adapter, to the handset jack mounted in the telephone base. The handset and handset cord are also connected to the adapter, and the user may, by operating a switch on the adapter, use the phone line for voice or data communications.
However, when in a data communication mode, the adapters of this sort must include conversion circuitry that interfaces the two wires of the modem with the four wires of the telephone handset jackxe2x80x94essentially duplicating the function already performed in the telephone base. Consequently, these adapters require additional circuit components and an independent power supply, thereby resulting in an adapter which has a higher overall cost. Further, to accommodate the additional conversion circuitry, the adapter is necessarily larger and bulkierxe2x80x94a characteristic that is particularly inconvenient to users of portable computers.
In addition, the prior art adapters allow a modem to connect to any one of many different types of telephone sets. As such, the adapters include circuitry that regulates the voltage level of the transmit signal (i.e., the xe2x80x9cvolumexe2x80x9d of the signal) that is generated by the modem and supplied to the telephone base. This is done to avoid problems such as feedback, signal distortion and signal loss, and to insure that the data signals generated by the modem are accurately transferred to the telephone line after passing through the telephone base. This voltage level is typically adjusted by way of a manual switch and circuit arrangement. Again, this approach necessarily results in a costlier, more complex, and physically larger adapter. Further, manual adjustment of the transmit signal amplitude may not be sufficiently precise, and could potentially result in loss of dataxe2x80x94especially at the high transmission speeds of today""s modems.
Finally, in order to establish a data communications link with adapters of this type, a precise sequence must be followed by the modem user. Typically, the user must first insure that adapter is properly connected to the computer modem and then set the transmit xe2x80x9cvolumexe2x80x9d level to one that corresponds with the type of telephone set being used. The user must then remove the handset from the phone base cradle and listen for a dial tone. The user must then immediately cause the modem to dial a phone number, or risk losing the dial tone. If the sequence is deviated from at any step, the modem will not be able to establish a communication link, and the process must be repeated. As will be appreciated, this approach can be confusing to many modem users, and often is the source of error when attempting to establish a data communication link.
The present invention has been developed in response to the present state of the art, and in particular, in response to these and other problems and needs that have not been fully or completely solved by currently available adapters for connecting computer modems to a telephone line via a telephone set. Thus, it is an overall object of the present invention to provide an apparatus, system and method for reliably connecting and for interfacing a communication device, such as a computer modem, with a telephone line so as to provide for data or voice communications on the single line.
Another object of the present invention is to provide a connection system and method which allows a communication device to be connected to a PBX controlled telephone line.
It is another object of the present invention to provide a connection system and method which allows a communication device to be connected to a telephone line via varying types of telephone sets.
Yet another object of the present invention is to provide a connection system and method which utilizes a minimum number of circuit components, thereby resulting in a connection system which is reliable, inexpensive, small in size, and conducive for use with portable computers and modems.
A further object of the present invention is to provide a connection system which is programmably monitored and controlled, and therefore easy to use.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
Briefly summarized, the foregoing and other objects are achieved with a novel and improved apparatus, system and method for connecting and for interfacing a communication device, such as a computer modem, to a two-wire telephone line via an existing telephone set, thereby allowing for data or voice communications on the single telephone line. In one preferred embodiment, the present invention includes an interface circuit, disposed within an interface adapter, for connecting the modem to the telephone set. The interface circuit preferably includes a four-wire handset connector jack for connecting to the handset portion of a standard telephone set, which includes a pair of handset transmitting wires (i.e., microphone lines) and the pair of handset receiving wires (i.e., speaker lines). Also included on the interface circuit is a four-wire base connector jack for connecting directly to the four-wire handset jack that is mounted on the telephone base (and which ordinarily receives the handset) via a four-wire base interconnect cable. Finally, the interface circuit in a preferred embodiment includes a data jack for connecting directly to the modem via a communication device interconnect cable. Thus, in one preferred embodiment the modem, the telephone handset, and the telephone base are all simultaneously coupled into the interface circuit.
A modem (or similar communication device) typically has a single pair of communication leads or wires, often referred to as the tip and ring lines, that match up with a corresponding pair of leads in a telephone line. However, in a preferred embodiment of the connection system of the present invention the modem is provided with a pair of transmitting wires and a pair of receiving wires that correspond directly with the four wires present within the handset connector jack of the telephone base. Thus, when in a data transmission mode, the interface circuit directly connects the two pairs of wires within the modem to the corresponding two pairs of wires within the telephone base/handset connector. In this way, there is no need for the interface circuit to provide a two-wire to four-wire conversion when transmitting a data signal, or a four-wire to two-wire conversion when receiving a data signal. Rather, as is well known, the telephone base, which is connected to the two-wire telephone line, performs the necessary signal conversions. Thus, in a preferred embodiment, the circuitry within the interface adapter utilizes few circuit components, is inexpensive and reliable, can be implemented in an extremely small physical space, does not require an external power supply, and results in an adapter that is generally less complex than interface adapters previously available.
To switch between a voice mode and a data mode state, the interface circuit portion of the connection system preferably includes a relay means. Preferably, the relay means automatically switches between the voice mode and the data mode, depending on the manner by which the single phone line is to be utilized. Thus, when in a voice mode state, the relay means causes the pair of handset transmitting wires and the pair of handset receiving wires to be electrically coupled directly to the corresponding pair of base transmitting wires and base receiving wires, and the telephone base and handset can be used for normal voice communication. Conversely, when in the data mode state, the relay means functions so as to electrically couple the pair of modem transmitting wires and the pair of modem receiving wires with the corresponding pair of base transmitting wires and base receiving wires. In this state, the modem can transmit and receive data signals to the telephone line via the interface adapter.
In another preferred embodiment, the present invention includes an interface circuit, disposed within an interface adapter, for connecting the modem to the telephone set. The interface circuit preferably includes a four-wire base connector jack for connecting directly to the four-wire handset jack that is mounted on the telephone base which ordinarily receives the four-wire base interconnect cable between the telephone base and the handset. Finally, the interface circuit in the present embodiment includes a data jack for connecting directly to the modem. In the present embodiment, only the telephone base, and not the handset, interfaces with the modern The data jack for connecting directly to the modem is configured for compatibility with a wireless or cellular interface located on the modem Traditional cellular or wireless interfaces are comprised of single-ended transmit and receive signals. Also included within the interface circuit are single-ended converters for compatibly interfacing the cellular or wireless interface of the modem with the four-wire telephone base jack.
In a preferred embodiment, the connection system also includes a cable detector function. The cable detector comprises circuitry that detects whether the modem is electrically connected to the interface adapter circuitry. Preferably, the cable detector circuitry generates a cable detection signal, the status of which can then be monitored by the communications software that is being executed on the host computer that is coupled to the modem. In this way, the connection status of the modem is programmable monitored, thereby allowing the host computer to automatically initiate and prompt the modem user to use the proper sequence for establishing a data communications link. This simplifies the overall operation of the connection system.
In a preferred embodiment, the interface adapter is utilized in conjunction with a host computer, which is operatively coupled to the modem or a similar communications device. Typically, the host computer includes a computer input device, such as a keyboard and/or a pointing device, a computer display and a programmable host processor. In use, a modem typically transmits signals to the telephone line that have a fixed voltage level, or transmit volume. However, when connected to a telephone base, the modem must adjust the transmit volume so that it conforms with the operating characteristics of the phone base, which can vary from type to type. To address this need, in one preferred method of the present invention, the programmable host processor is programmed so as to cause a communication processor located on the modem to transmit outgoing data signals at a preselected voltage level (i.e., transmit volume) that corresponds to the particular type of telephone base being used. In one embodiment, this preselected voltage level corresponds to a selection made by the user from a menu of telephone set types that are displayed on the computer""s display. This approach eliminates the need for a manual switch and corresponding circuit arrangement for selecting a voltage level for outgoing data signals. Further, because it is done programmably, the amplitude of the transmit signal can be adjusted very precisely so as to match exactly the requirements of the particular telephone set, thereby insuring the accuracy of the outgoing transmit data.
In yet another preferred embodiment of the present invention, the transmit volume level used by the modem to transmit outgoing data signals is automatically calculated for the particular telephone set being used, thereby eliminating the need for any user intervention. Under this approach, the programmable host processor is programmed so as to cause the appropriate executable instructions to be invoked at the modem communication processor that function so as to automatically determine the optimum transmit level to be used for the particular telephone set being used. Preferably, this is accomplished by sending a transmit signal to the telephone base, and then monitoring the resulting receive signal via the telephone base sideband frequency. The amplitude (volume or gain level) of the transmit signal is then increased by iterative amounts, until the signal on the receive line is distorted or of unacceptable quality, i.e., thereby indicating that the telephone base amplifier has started to clip the signal and the volume level is too high for that particular telephone set. At this point, the amplitude level of the last used transmit signal is reduced by a predetermined amount, and the new value is deemed to be the optimum transmit level volume for that particular telephone set.
By utilizing the preferred program method of the present invention, the series of steps that a computer user is to follow when establishing a data communications link via a telephone base are displayed on the computer display, and thereafter monitored and controlled via the programmable host processor. This simplifies the overall connection process, and enables a user to establish a data communication link in a quicker and less confusing manner.